1. Field of the Invention
This invention relates to components for electronic packages. More particularly, there are provided metallic substrates and heat sinks useful in ball grid array electronic packages.
2. Description of Related Art
Microelectronic devices are typically manufactured from a semiconductor material such as silicon, germanium or gallium/arsenide. The semiconductor material is fashioned into a die, a generally rectangular structure having circuitry formed on one surface. Along the periphery of that electrically active surface are input/output pads to facilitate electrical interconnection to external circuitry.
The semiconductor device is brittle and requires protection from moisture and mechanical damage. This protection is provided by an electronic package. The electronic package further contains an electrically conductive means to transport electrical signals between the semiconductor device and the external circuitry.
One electronic package is disclosed in U.S. Pat. No. 4,939,316 to Mahulikar et al, which is incorporated by reference in its entirety herein. The patent discloses separate anodized aluminum or aluminum alloy base and cover components defining a cavity. A leadframe is disposed between the base and the cover and adhesively bonded to both. A semiconductor device is encased within the cavity and electrically interconnected to the inner lead ends of the leadframe. The outer lead ends of the leadframe extend beyond the package perimeter and are interconnected to external circuitry.
The available space on a printed circuit board is limited and it is desirable to minimize the peripheral area of a package. The peripheral area of a leaded package extends beyond the perimeter of the package base and cover to a point defined by the outer lead portions of the leadframe.
To minimize the peripheral area of an electronic package, electrical interconnection may be through a package component as disclosed in U.S. patent application Ser. No. 08/033,596, entitled "Ball Grid Array Electronic Package" by Mahulikar et al that was filed on Mar. 19, 1993 and is incorporated by reference in its entirety herein. The ball grid array package has a metallic base coated with an electrically non-conductive layer. Conductive vias extend through apertures formed through the base. One end of the via is electrically interconnected to the semiconductor device and the other end is bonded to a solder ball for attachment to external circuitry.
In U.S. patent application Ser. No. 08/277,387 entitled "Integrally Bumped Electronic Package Components" by Deepak Mahulikar et al, that was filed Jul. 19, 1994 and is incorporated by reference in its entirety herein, ball grid array electronic packages are disclosed that do not require vias extending through a metallic substrate. The metallic substrate is coated with an electrically non-conductive layer and circuit traces are formed on this electrically non-conductive layer to electrically interconnect a semiconductor device to external solder balls.
While the ball grid array electronic packages disclosed in the above patent applications have proven satisfactory, the Applicants have developed electronic package components that improve the electrical properties, the thermal characteristics and the reliability of the package.